The Zaporizhzhia Nuclear Power Plant in Ukraine was shut down (roughly) 1000 days ago, so no "new" radioactivity is being produced, and the radioactivity in the re-actors is decaying away. Use the half-life values in Appendix F for your calculations, and you can use the isotope A for the atomic mass when calculating "how many moles?".
With 10kg of ¹²⁷xe in the reactor cores when the plant was shut down, how much is present now?
